Circuits to control and drive brushless DC (BLDC) electric motors are known. Conventionally, the circuits provide one function signal from which a plurality motor drive signals, each at a different phase, are derived.
Some known electric motor drive circuits are described in U.S. Pat. No. 7,590,334, issued Sep. 15, 2009, U.S. Pat. No. 7,747,146, issued Jun. 29, 2010, and U.S. patent application Ser. No. 13/271,723, filed Oct. 12, 2011 and entitled “Electronic Circuit And Method Generating Electric Motor Drive Signals Having Phase Advances In Accordance With A User Selected Relationship Between Rotational Speed Of An Electric Motor And The Phase Advances,” each of which is assigned to the assignee of the present invention.
A BLDC electric motor can exhibit jitter it its speed of rotation when driven by a conventional motor drive circuit. In some applications, for example, motors used in printers, for example, inkjet printers, can experience an undesirable amount of jitter. In these particular applications, the jitter results in printing clarity reduction.
The amount of jitter in the rotational speed of electric motor driven by conventional motor control circuit is related to the fact that the above-described function signal within the motor control circuit does not necessarily align with the motor rotations such that an exact number of cycles of the function signal is achieved for each rotation of the motor.
In view of the above, it would be desirable to provide a motor control circuit and associated method that can generate electric motor drive signals to more accurately control, more accurately than a conventional motor control circuit, the speed of rotation of an electric motor, thereby reducing jitter in the rotational speed of the electric motor. It would also be desirable to provide a motor control circuit that can drive the motor at a rotational speed synchronized with an external clock signal received by the motor control circuit.